3.16.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Francesco Ruggeri fruggeri@arista.com
commit 833a426cc471b6088011b3d67f1dc4e147614647 upstream.
acpi_os_map_cleanup checks map->refcount outside of acpi_ioremap_lock before freeing the map. This creates a race condition the can result in the map being freed more than once. A panic can be caused by running
for ((i=0; i<10; i++)) do for ((j=0; j<100000; j++)) do cat /sys/firmware/acpi/tables/data/BERT >/dev/null done & done
This patch makes sure that only the process that drops the reference to 0 does the freeing.
Fixes: b7c1fadd6c2e ("ACPI: Do not use krefs under a mutex in osl.c") Signed-off-by: Francesco Ruggeri fruggeri@arista.com Reviewed-by: Dmitry Safonov 0x7f454c46@gmail.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/acpi/osl.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-)
--- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -416,24 +416,27 @@ acpi_os_map_memory(acpi_physical_address } EXPORT_SYMBOL_GPL(acpi_os_map_memory);
-static void acpi_os_drop_map_ref(struct acpi_ioremap *map) +/* Must be called with mutex_lock(&acpi_ioremap_lock) */ +static unsigned long acpi_os_drop_map_ref(struct acpi_ioremap *map) { - if (!--map->refcount) + unsigned long refcount = --map->refcount; + + if (!refcount) list_del_rcu(&map->list); + return refcount; }
static void acpi_os_map_cleanup(struct acpi_ioremap *map) { - if (!map->refcount) { - synchronize_rcu_expedited(); - acpi_unmap(map->phys, map->virt); - kfree(map); - } + synchronize_rcu_expedited(); + acpi_unmap(map->phys, map->virt); + kfree(map); }
void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size) { struct acpi_ioremap *map; + unsigned long refcount;
if (!acpi_gbl_permanent_mmap) { __acpi_unmap_table(virt, size); @@ -447,10 +450,11 @@ void __ref acpi_os_unmap_iomem(void __io WARN(true, PREFIX "%s: bad address %p\n", __func__, virt); return; } - acpi_os_drop_map_ref(map); + refcount = acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock);
- acpi_os_map_cleanup(map); + if (!refcount) + acpi_os_map_cleanup(map); } EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem);
@@ -491,6 +495,7 @@ void acpi_os_unmap_generic_address(struc { u64 addr; struct acpi_ioremap *map; + unsigned long refcount;
if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) return; @@ -506,10 +511,11 @@ void acpi_os_unmap_generic_address(struc mutex_unlock(&acpi_ioremap_lock); return; } - acpi_os_drop_map_ref(map); + refcount = acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock);
- acpi_os_map_cleanup(map); + if (!refcount) + acpi_os_map_cleanup(map); } EXPORT_SYMBOL(acpi_os_unmap_generic_address);